The prior art discloses a number of ways to achieve multi-wavelength laser transmission.
United States Patent Application Publication 2010/0220753, for example, concerns a monofrequency, intra-cavity, frequency-tripled, continuous laser. This assembly is a diode-pumped device. It includes an amplifying medium, two birefringent non-linear mediums for frequency doubling and tripling, and a polarizing medium used as a Lyot filter adapted to allow monofrequency output emission.
This invention, US 2010/0220753, is a method for generation of a Continuous Wave (CW), monofrequency UV laser source using intra-cavity, temperature controlled, birefringent non-linear converters, driven by a Nd based diode pumped laser operating at ˜1 μm.
United States Patent Application Publication 2010/0142962 involves a multiwavelength transmitter comprised of several laser sources and electroabsorption modulators. The lasers are configured to generate differing wavelengths and the modulators are configured to match the lasers, modulating one corresponding wavelength.
U.S. Pat. No. 7,792,162 features a selectable multiwavelength laser for outputting visible light. This assembly is comprised of a laser capable of producing multiple wavelengths simultaneously to resonate in a cavity. One of the frequencies is generated by a Raman crystal. A tunable non-linear medium is positioned within the cavity for frequency conversion, and a tuner is used to tune it to select a wavelength for conversion. The output beam from this assembly is used for treatment, detection, and diagnosis of patients in ophthalmology and dermatology.
Comprised of a single gain element, Q-Switch, and multiple intra-cavity non-linear converters, using both folded and liner cavity configurations with multiple partially reflective output mirrors to outcouple laser light of varying wavelengths, this invention, U.S. Pat. No. 7,792,162, is optically complex, requires removal and replacement of various intra-cavity, elements to achieve particular sets of multiple wavelengths, and in each case requires a combination of angle and/or temperature tuning to attain specific wavelengths.
U.S. Pat. No. 6,356,088 concerns a compact laser scanning microscope with an integrated short-pulse laser. This assembly is useful for multiphoton microscopy for three-dimensionally resolved microscopic analysis because it circumvents optical direct coupling and fiber coupling. It is used for analysis of materials, particularly for optical beam induced current analysis.
U.S. Pat. No. 6,356,088 utilizes multiple wavelengths using lasers sources in ultrafast regime which are combined and converted with various non-linear converters similar to that described in U.S. Pat. No. 7,792,162 but configures the laser to be consistent with small volume packaging for an advanced compact laser scanning microscope.
An improved way, however, is still necessary to achieve better laser beam quality using fewer parts while allowing for a decrease in the size of the transmit aperture.